Hello Kattamann!
Great to have you with us!
When you want to configure your machine as Tor entry for censored users, you need to set up Vidalia as Bridge.
Download the Vidalia bridge bundle from https://www.torproject.org/download/download.html.en
More information you find in the manual or on https://www.torproject.org/docs/bridges
Somewhat more advanced is an obfuscated bridge https://www.torproject.org/projects/obfsproxy.html what works against the censorship of normal bridges.
I recommend to read a little bit about Tor to get a better understanding.
When you want to run the bridge on your main PC, it shall be "always on". But be careful: As bridge operator you run a real server, with all risks of a machine, which is always on the net and listening for incoming connections. You should inform yourself at least about firewalls and the port-forwarding on your modem/router, so that external users can reach you bridge.
After getting some experience with the bridge it might be better to switch to a small singleboard computer like the RaspberryPi, OLinuXino or Wandboard. They cost only little, consume less electricity like a desktop and do not contain you personal data. You can connect them directly to the modem.
Best Regards
Anton